CORTICOSTERONE EFFECTS ON CORTICOTROPIN-RELEASING HORMONE MESSENGER-RNA IN THE CENTRAL NUCLEUS OF THE AMYGDALA AND THE PARVOCELLULAR REGIONOF THE PARAVENTRICULAR NUCLEUS OF THE HYPOTHALAMUS

Using in situ hybridization histochemistry, we report differential exp ression of corticotropin-releasing hormone (CRH) mRNA in the central n ucleus of the amygdala (CEA) and the parvocellular region of the parav entricular nucleus of the hypothalamus (PVN) following systemic treatm ent with corticosterone (CORT) in adrenally-intact rats. Both injectio n of low (1 mg/kg/day) and high (5 mg/day) CORT reduced CRH mRNA expre ssion in the PVN in a dose-dependent manner, although it returned to n ormal at the low dose by 14 days. By contrast, the high dose of CORT i ncreased CRH mRNA transiently in the CEA at 4 days, although the low d ose of CORT decreased it at 14 days. In a second experiment, we implan ted a slowly-releasing CORT pellet for 2 weeks (200 mg, 60 day release ) subcutaneously. This treatment produced an elevation of CRH mRNA in the CEA both at 1 and 2 weeks, whereas CRH mRNA in the PVN was decreas ed to a large extent as seen in the high CORT group of the first exper iment. These results suggest that glucocorticoids can facilitate CRH m RNA expression in the CEA, a site implicated in anxiety and fear, whil e restraining the hypothalamic-pituitary-adrenal axis as indicated by the reduction in CRH mRNA in the PVN.